For controlling several AV devices within a network of home entertainment products the so-called HAVi (Home Audio Video Interoperability) standard has been developed. This standard specifies the control of television sets, video recorders, set top boxes and other devices, especially for the control of the exchange of digital audio and video streams. The devices are connected via the IEEE 1394 bus (i.LINK® or Fire-Wire®), which has enough capacity to simultaneously carry multiple digital audio and video streams.
Each device added to the HAVi network automatically installs its own application and interface software and is automatically registered by the system so that other devices know what it is capable of. So-called Application Programming Interfaces of the most common AV functions have been standardized. Furthermore, functions on a device within the HAVi networking system may be controlled from another device within the system.
HAVi defines two different ways of using User-Interfaces (UIs). Both solutions are working in principle in the same way: one device within the network (target) provide UI-elements or a kind of a complete UI to a display device (controller). The controller renders the UI-elements or executes the complete UI, respectively. The first mode is called Data Driven Interaction (DDI), the second one UI by havlets.
For a DDI-UI a part of a network is shown in FIG. 1. A display device 1 and a controlled device 3 are connected via an IEEE 1394 bus 5. The target device in the IEEE1394 network comprises a Device Control Module (DCM) 4, which can provide DDI-elements to the network for creating a UI. It is also able to control the device, natively, by commands.
Because a DCM is registered within the HAVi network, a DDI controller 2 can “subscribe” to the DCM 4. This is the start of an interaction between the DDI controller 2 and the DCM 4 to transmit the DDI-elements to the controller, display them to the user and afterwards to translate the user's action on these DDI-elements to native commands in the DCM.